Please cite an official document that shows the US government forcing GitHub to secretly modify the source code of a project in one of its repos.
As far as I'm aware, they've literally never done that, and to suggest they have means you have to show evidence that such a thing has taken place.
This is some Fox News level bullshit. "How do we know the FBI hasn't raped and murdered a girl in 1990? They've never come out and specifically stated they haven't!"